This application incorporates by reference Taiwan application Serial No. 090110667, filed May 3, 2001.
1. Field of the Invention
The invention relates in general to an image output device, and more particularly to an image output device for improving image resolution and tone expression.
2. Description of the Related Art
In recent years, the personal computer has become so popular that the peripheral computer products have developed very rapidly. Most users employ printers to create output images by printing the electrical documents, such as plain text, colorful graphics, or beautiful pictures, which might be downloaded from the Internet or photographed by a digital camera. By balancing the price and quality, the color ink-jet printer is an affordable option for most PC buyers and has thus become the most popular type of printer sold today.
In the ink-jet printer, a print head traverses over the surface of the paper and ejects ink onto the paper to form a printed image. The bubble jet and piezoelectric print head technologies are widely applied to ink-jet printers now to produce bubble jet printers and piezoelectric printers. The principal difference between bubble-jet printers and piezoelectric printers is that bubble-jet printers use special heating elements to prepare the ink, and the piezoelectric printers use piezoelectric crystals. In substance, the piezoelectric printer uses the expanding piezoelectric crystals to force ink drops out of the nozzle and onto the paper. Usually, the bubble jet printer includes a heating element, ink, and nozzle. The heating element heats the ink and forms a bubble until the pressure forces it to burst. A drop of ink is then forced out of the nozzle and onto the paper. During printing, it is required that the ink density and dropping location be controlled to form the desired printed image.
The printed image is a pattern consisting of a number of ink drops or pixels. The print quality relates to the resolution. Generally speaking, the higher the resolution, the more pixels per square inch an image has, and the better the overall print quality. For example, if the resolution of 600*600 dpi (dot per inch) increases to the resolution of 1200*600 dpi, the ink drop size decreases a half time accordingly. The U.S. Pat. No. 5,726,690 discloses a method for controlling the ink drop size by controlling the pulse width of the delivered firing pulse. However, the variation range of the ink drop size is only 16% by the method, which does not improve the resolution very much.
Another key factor of print quality for a color ink-jet printer is the tone expression. The traditional color ink-jet printer uses ink of four colors, M (Magenta), C (Cyan), Y (Yellow), and K (Black). In recent years, the color ink-jet printer uses ink of six colors including M, C, Y, K, light M, and light C, or even uses ink of seven colors by adding light Y. Therefore, the tone expression can enrich the color of the printed image. In a printer having six color inks, the printed image can have 25=32 kinds of color combinations without the shortcoming of half tone simulation and the print quality will greatly improve. Therefore, the key factor of print quality for a color ink-jet printer is the number of the color combinations, that is to say, the tone expression.
The following statement is about the improvement on the variation range of the ink drop size (resolution) and the number of the color combination (tone expression) regarding the conventional image output device with ink of four/six colors.
Referring to FIG. 1, an arrangement for a nozzle of the conventional image output device with ink of four colors is shown. The conventional image output device with ink of four colors includes a color ink cartridge 110 and a black ink cartridge 140. The color ink cartridge 110 has a yellow ink tank Y filled with yellow ink 112, magenta ink tank M filled with magenta ink 114, and cyan ink tank C filled with cyan ink 116. The small circles near the ink tanks represent the nozzle of the printhead for ejecting ink. The yellow ink nozzle 122 is capable of ejecting yellow ink 112, the magenta ink nozzle 124 is capable of ejecting magenta ink 114, and the cyan ink nozzle 126 is capable of ejecting cyan ink 116. The black ink cartridge 140 only has a black ink tank K filled with the black ink 142, and the black ink nozzle 152 is capable ejecting black ink 142.
Referring to FIG. 2, another arrangement for nozzle of the conventional image output device with ink of four colors is shown. The U.S. Pat. No. 6,149,260 discloses an ink jet recording apparatus capable of printing different dot sizes by using a large size nozzle and a small size nozzle to increase the variation range of the ink drop size. As shown in FIG. 2, the conventional image output device with ink of four colors includes a color ink cartridge 210 and a black ink cartridge 240. The color ink cartridge 210 has a yellow ink tank Y filled with yellow ink 212, magenta ink tank M filled with magenta ink 214, and cyan ink tank C filled with cyan ink 216. The yellow ink nozzles 222, 232 are capable of ejecting yellow ink 212, the magenta ink nozzles 224, 234 are capable of ejecting magenta ink 214, and the cyan ink nozzles 226, 236 are capable of ejecting cyan ink 216. The black ink cartridge 240 only has a black ink tank K filled with the black ink 242, and the black ink nozzle 252 is capable ejecting black ink 242.
In FIG. 2, the color cartridge 210 has nozzles with a large diameter and a small diameter. The nozzle with small diameter will be driven to eject the small ink drop or light ink drop. The nozzle with large diameter will be driven to eject the large ink drop or dark ink drop. The ejected ink has a proper size and color since the variation range of the ink drop size is increased. However, it requires a larger wafer for forming nozzles with different diameters on one printhead. Besides, the cost of manufacturing the printhead increases and the controlling method becomes more complicated. Although the ink jet recording apparatus is capable of printing in different dot sizes by using two nozzles with different sizes increases the variation range of the ink drop size, it increases the cost of manufacturing the printhead and the complexity of controlling the printhead.
Referring to FIG. 3, an arrangement for nozzles of the conventional image output device with ink of six colors is shown. The conventional image output device with ink of six colors includes color ink cartridges 310 and 340. The color ink cartridge 310 has a yellow ink tank Y filled with yellow ink 312, magenta ink tank M filled with magenta ink 314, and cyan ink tank C filled with cyan ink 316. The yellow ink nozzle 322 is capable of ejecting yellow ink 312, the magenta ink nozzle 324 is capable of ejecting magenta ink 314, and the cyan ink nozzle 326 is capable of ejecting cyan ink 316. The color ink cartridge 340 has a black ink tank K filled with the black ink 342, light cyan ink tank c filled with cyan ink 344, and light magenta ink tank m filled with light magenta ink 346. The black ink nozzle 352 is capable of ejecting black ink 342, the cyan ink nozzle 354 is capable of ejecting cyan ink 344, and light magenta ink nozzle 356 is capable of ejecting magenta ink 346.
Comparing FIG. 3 with FIG. 1, the light cyan ink and the light magenta ink are included in the color ink cartridge 340. This increases the tone expression and therefore enriches the color of the printed image. However, the variation range of the ink drop sizes is limited due to the uniform size of the nozzles. It is still of no help to improve image resolution.
It is therefore an object of the invention to provide an image output device for improving image resolution and tone expression by the arrangement for nozzles of the color ink cartridge of the image output device.
The invention achieves the above-identified objects by providing an image output device includes two color ink cartridges. The first color ink cartridge has a yellow ink tank Y filled with yellow ink, a first magenta ink tank M filled with magenta ink, and a first cyan ink tank C filled with cyan ink. Besides, the yellow ink nozzle is connected with the yellow ink tank Y for ejecting the yellow ink, the first magenta ink nozzle is connected with the first magenta ink tank M for ejecting the magenta ink, and the first cyan ink nozzle is connected with the first cyan ink tank C for ejecting the cyan ink. The second color ink cartridge has a black ink tank K filled with black ink, a second magenta ink tank M filled with magenta ink, and a second cyan ink tank C filled with cyan ink. Besides, the black ink nozzle is connected with the black ink tank K for ejecting the black ink, the second cyan ink nozzle is connected with the second cyan ink tank C for ejecting the cyan ink, and the second magenta ink nozzle is connected with the second magenta ink tank M for ejecting the magenta ink. When employing the image output device for printing, the color ink cartridge ink having nozzle with small diameter is driven to create small ink drops or light ink drops, and the color ink cartridge having nozzle with large diameter driven to create large ink drops or dark ink drops.
Furthermore, the image output device can have two ink color cartridge, both of which provides yellow ink, magenta ink, and cyan ink to achieve the same result by simply using different diameters of the nozzles. The image output device in the invention improves the image resolution and create a six-color tone expression. Moreover, the cost of manufacturing the printhead will not be increased and the controlling method will not become complicated.
Other objects, features, and advantages of the invention will become apparent from the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings.